Band saws are extremely dangerous machines. With even the slightest momentary inadvertent movement, the operator of a band saw may face serious and debilitating injury. The potential for this human suffering and serious personal injury arises from the fact that a band saw is always operated with a portion of the blade's sawing length unguarded in order to cut workpieces. Moreover, the nature of a band saw is such that the operator necessarily places his arms, hands and fingers precariously close to the unguarded band saw teeth.
The teeth of a band saw usually face the operator. The operator cuts a workpiece by placing it between himself and the teeth, and sliding the workpiece toward and through the teeth until the workpiece has been completely cut. In order to accommodate large workpieces, the band saw must be able to have a large number of teeth exposed. When the saw is being used to cut small workpieces, however, it is desirable for the operator's safety to have only a limited length of blade exposed. Indeed, whatever the size of the workpiece being cut, it is desirable to have a minimal length of blade exposed, i.e. only the length of blade necessary to cut the entire workpiece.
Most band saw blade guards in the prior art are adjustable, in that they allow the operator to reduce the amount of blade exposed to only that necessary to accommodate the workpiece being cut.
This active, operator dependent adjustment, however, depends upon the skill, training, competence and concentration of the operator. Thus, if the operator is rushed, tired, or has a foreseeable lapse of concentration, he may not adjust the blade guard to minimize the exposed area or in attempting to adjust the guard, he may not properly complete this task. The operator may cut a small workpiece on a band saw while a large length of blade is exposed, particularly given the pressures of production or the stresses of a job shop environment.
The band saw teeth, designed to cut through wood, steel and other materials, can similarly cut human body parts. Only the slightest momentary contact with a limb or body part is necessary to cause serious and permanent injury, because the unidirectional cutting nature of the band saw can operate to pull an object into the cutting path with even the slightest contact. Furthermore, if an unfortunate operator should mistakenly allow his gloved hand or sleeve to contact the band saw blade, his hand or wrist will inevitably follow.
The foreseeable dangers inherent in the operation of any band saw compel the use of a safety guard, or some other form of safety system for the band saw during operation, in order to protect the operator.
The nature of the dangers of a band saw further require that a safety guard or safety system be fail-safe and "passive", or "fool-proof", if possible. To be fully effective, the safety system must operate automatically and passively, without the need for operator intervention or adjustment. Moreover, the safety system must be such that the band saw operation is precluded without the safety system being in place.
Many band saw operators are untrained and unsophisticated with respect to safety matters and the significant and foreseeable risks of harm attendant to the exposed band saw blade. Safety instructions, although often provided with band saws, are not sufficient to protect band saw operators if the hazards can be properly guarded. Typically, safety instructions and/or warnings are provided with a band saw wherein the user is instructed to adjust the upper blade guard in a downward direction until a minimum clearance is provided between the bottom of the upper blade guard and the top of the object being cut. The band saw operator is then requested to lock in place, generally by a cam actuated handle, the upper blade guard in its preferred/desired location. Such safety instructions place a continuing, on-going burden upon all band saw operators to constantly manually adjust the band saw upper blade guard to minimize the amount of exposed blade and danger zone, when cutting different thicknesses of material. The efficacy of implementing a safe product through such safety instructions and/or warnings is foreseeably inadequate when a competent mechanical guarding system can be implemented. The consequence of relying solely upon such instructions and/or warnings, is foreseeable and inevitable injuries given the reality of human factors.
Thus, while the manually operated blade guard may be sufficient for some operators and in some circumstances, it is also foreseeably insufficient in others. However, to be effective, a guarding system cannot be arbitrary and operate only for selected circumstances, but it must safeguard all foreseeable users as well as safeguard against all foreseeable uses and misuses of the band saw wherever possible.
The foreseeable and significant hazards associated with operation of such a band saw are numerous. For example, if an operator utilizes the band saw with an exposed area larger than the workpiece, the blade will be exposed to his arms, face and hands as he or she pushes the workpiece past the blade.
Heretofore, because of the design of the equipment, the dangers of the exposed blade could only be cured by the operator. Even though injuries were foreseeable, band saw manufacturers did not ensure that the operators would always utilize the band saws leaving the proper allowable distance of exposed band saw blades. In industrial operations, it is foreseeable that there may be multiple users of band saws. The blade guard adjustment set by a previous operator may be maintained by a subsequent operator even if that previous operator were cutting larger workpieces. It is foreseeable that with a large blade exposure while pushing small workpieces past the blade, the operator's hands or fingers may inadvertently slip into the danger zone, i.e. the exposed blade zone, and to the teeth of the rapidly moving blade.
In addition, with the upper blade guard in a raised position, the guide rollers attached to this lower blade guard will be at an extended location from the workpieces. This will permit increased workpiece vibration, and lateral and rotational motion of the blade resulting in decreased sawing efficiency. This decreased sawing efficiency may cause the operator to grasp the workpiece closer to the blade and to push the workpiece into the blade with greater force. The closer proximity of the worker's hand to the moving blade and/or increasing the force applied to the workpiece in crease the hazards of the band sawing operation.
Finally, it may often happen that many operators of the band saw either lack training, or lack understanding, of the safe and proper way to operate the hazardous band saw. They may also be unaware of the potential dangers and therefore be unlikely to seek assistance in the band saw operation. This is particularly true since many users may be lulled into a false sense of security by the deceptively benign or harmless appearance of a band saw in operation.